Denso 221-3511 Radiator

Denso Radiator for Mazda 6 Cooling Service

Denso 221-3511 is a radiator built for 2003-2005 Mazda 6 applications. It is configured with a 29.0000-inch core width, 14.8750-inch core height, and 1.0000-inch core thickness, plus 1.2500-inch inlet and outlet diameters for direct cooling-system service.

This radiator includes a transmission oil cooler and is engineered to match OE-style fitment and cooling performance for Mazda 6 models across the 2003, 2004, and 2005 model years. Denso’s OE supply experience is reflected in the radiator’s tank, fin pitch, core dimensions, and material selection.

Key Features

• Part number: 221-3511
• Fits 2003-2005 Mazda 6
• Core height: 14.8750 in.
• Core width: 29.0000 in.
• Core thickness: 1.0000 in.
• Inlet diameter: 1.2500 in.
• Outlet diameter: 1.2500 in.
• Transmission oil cooler included
• OE-style radiator configuration for direct replacement service

Detailed Description

Denso 221-3511 is a replacement radiator for the Mazda 6, covering 2003-2005 model years. It is built around OE-based dimensions and cooling-system requirements, with a core size and hose connections that support proper coolant flow and heat transfer. For buyers searching for a 2003 Mazda 6 radiator, 2004 Mazda 6 radiator, or 2005 Mazda 6 radiator, this unit provides a direct-fit solution with the transmission oil cooler already integrated.

Denso’s radiator design process focuses on matching the original vehicle layout, including tank design, fin pitch, core dimensions, and materials. That approach helps maintain consistent engine cooling performance in daily driving and demanding operating conditions. This part cross-references Spectra Premium CU2673 and CSF 2991 for the same application.

Common Problems This Radiator Can Address

• Overheating caused by a leaking or restricted radiator
• Coolant loss from cracked tanks or damaged core passages
• Poor heat rejection from an aging Mazda 6 cooling system
• Transmission fluid temperature control concerns when the factory cooler is part of the radiator assembly
• Fitment issues when replacing a worn OE radiator on 2003-2005 Mazda 6 models

Installation Notes and Tips

Verify hose diameter, core dimensions, and transmission cooler line routing before installation. Flush the cooling system, inspect the radiator cap, hoses, and thermostat, and refill with the correct coolant mixture after installation. Confirm that the radiator mounts and fan shroud alignment match the vehicle before final assembly.

Quality Assurance

Denso supplies radiators to OE car makers worldwide, and this radiator is built to meet OE manufacturer standards for durability and function. Each unit is tested for performance and reliability before release.